The present invention relates to an automatic bleed valve. It is especially suitable for attachment to the inlet manifold of an internal combustion engine.
The principle of "air bleed" has been known for many years. This principle states that allowing a small amount of additional air into the inlet manifold of an internal combustion engine at times of particularly low pressure (high vacuum), for example during moments of acceleration or deceleration of the engine, will allow significantly more efficient fuel burning within the engine. This should, in theory, reduce the emission of pollutants such as carbon monoxide (CO) and unburnt hydrocarbons (HC). However, to the knowledge of the inventor, no commercially useful embodiment of this principle has been produced. This is essentially because the reaction time of a bleed air supply must be extremely small in order to keep up with the variations in vacuum in the inlet manifold. As an example, the period for which air must be supplied is of the order of tens of milliseconds.
Early examples of this principle can be found in GB496409 from 1937 and GB690635 from 1950. Such devices do not appear to have become common in the field.
GB 2129869 and GB 2213875 propose arrangements in which a ball bearing-based non-return valve is arranged to supply bleed air to the inlet manifold. The ball bearing is biased towards a valve seat by a spring. However, the response time of these versions are lower than desirable, and in addition the. CO and HC reductions achieved are disappointing, even taking into account the lower response time.
In recent times, attention has been directed to computer based engine management systems (EMS). These are essentially microprocessors supplied with data from a number of sensors distributed around the engine. The EMS notes this data and compares it with preset data and/or algorithms and actively manages certain variables in order to optimise the fuel burning characteristics. However, such a system will inevitably be reactive in that an imbalance must first be detected and then corrected after it has existed for a certain period. Thus, the efficiency of such systems is inherently limited by their processing times.
Recent attention has therefore been directed to providing ever better response times for an existing EMS.